Precision measuring instrument



y 9 H. RUDOLPH 2,400,440

PRECISION MEASURING INSTRUMENT Filed Au '7, 1944 T 7 Z9 Z4 za m Z5 Patented May 14, 1946 PRECISION MEASURING INSTRUMENT Hans Rudolph, Kansas City, Mo. Application August 7, 1944, Serial No. 548,386 i -Claims. (Cl. sa-ivs) This invention relates to precision measuring instruments.

An object of this invention is'to provide an instrument for measuring interior diameters. 1

Another object of this invention is to provide I an instrument embodying a rigidshank orpilot which supports a movable finger or gauge member, with the latter extendible from a side of the shank or pilot by rotation of a calibrated operator.

With the foregoing objects and others which may hereinafter appear, the invention consists of the novel construction, combination and arrangement of parts as will be more specifically Figure 1 is a detail side elevation partly in longitudinal section of an internal precision measuring instrument constructed according to an embodiment of thisinvention.

Referring to the drawing, the numeral l0 designates generally an elongated body which is formed with an upper cylindrical part I an intermediate frusto-conical part I2 and a lower cylindrical part M which extends from the lower apex of the frusto-conical part l2. A handle I3 is disposed above the body [0 and is secured'to the upper part H by means of a bolt I4 having a reduced threaded lower end I5 which is threaded into the center of the upper part II.

The body I0 is provided with'an opening l6 which is disposed on an angle to the longitudinal axis of the body l0 and opens through the lower portion of the lower member l4. The opening l6 extends upwardly into the intermediate part l2 and communicates with an enlarged opening l1. The enlarged opening extends upwardly through the upper portion of the intermediate 7 part l2 and extends through the upper part II. A gauge pin I9 is slidable in the opening I6 being formed at its lower end with rounded face 20 which is dlsposedin the same plane as the longitudinal outer surface of the lower part l4.

The gauge pin I9 is provided at its upper end with an enlarged body 2| which is slidable in the enlarged opening l1 and the upper end of the enlarged body 2| terminates in a rounded head 22. The enlarged body 2| is formed with a longitudinally extending keyway 33 within which the inner end of a threaded pin extending through the upper part II is adapted'to engage, in order to hold the gauge pin l9 against rotary movement while permitting limited sliding movement thereof. A spring'25 is disposed in the opening I] bearing at its upper end against the lower end of the body 2| so as to constantly urge the pin i9 upwardly.

A gauge pin adjusting collar or member 26 is ithreaded onto the bolt [4 and is formed at its lower end with an annular sleeve or flange 21 adapted to telescope over the outer surface of the upper part I The upper part II is provided with a, plurality of longitudinally spaced apart gauge marks 28 andthe lower bevelled edge 29 of the annulus 21 is formed with a plurality of graduations-3il which are correlated with a longitudinal line 3| carried by the upper part II to determine the degree of extension of the pin l9 from the lower end of the gauge shank M. The upper end of the pin adjusting member 26 is formed with an annular flange 32 rotatably engaging about a lower enlargement or nut 33 which is carried by the handle i3 and into which the bolt or screw l4 threadably engages.

In the use and operation of the instrument, the shank I4 is extended into the opening which is to be measured, and the gauging pin. I 9 initially may be in its retracted position. When the shank I4 is within the opening in the workpiece, the pin projecting member 26 may be rotated on the bolt l4. Rotation of the pin projecting member 26 will force the pin l9 to an extended position with the gauging face or surface 20 projecting laterally of the shank M. The circumferential gauge marks 28 will determine roughly the size of the hole whereas the longitudinal gauge marks 33 will, in correlation with the gauge marks 30 carried by the adjusting member 26, determine the accurate size of the opening.

What I claim is:

1. A precision instrument comprising a shank for insertion into an opening in a workpiece, said 7 shank having an opening disposed on an angle to the length thereof and opening through one side adjacent one end of said shank, an elongated spring-pressed pin .slidable insaid latter openin said pin having the outer end thereof rounded to substantially the curvature of saidshank, and an enlarged body carried by the opposite end of said shank, said body having anopening disposed on an angle aligning with opening of said shank and said pin slidably extending into said body open- 2. A precision instrument comprising a shank for insertion into an opening in a workpiece, an

- enlarged body carried by one end of said shank,

by said body correlated with the graduations of said flange for indicating the diameter of the opening in the workpiece.

3. A precision measuring instrument as set 3 forth in claim 2, including means for holding said pin against rotary movement while permitting endwise movement thereof.

4. A precision measuring instrument as set forth in claim 2 wherein the outer end of said pin 10 is rounded and cut on an angle parallel with the longitudinal axis of saidshank. i

HANS RUDOLPH. 

